A237416 Smallest multiple of 5 beginning with n.

10, 20, 30, 40, 5, 60, 70, 80, 90, 10, 110, 120, 130, 140, 15, 160, 170, 180, 190, 20, 210, 220, 230, 240, 25, 260, 270, 280, 290, 30, 310, 320, 330, 340, 35, 360, 370, 380, 390, 40, 410, 420, 430, 440, 45, 460, 470, 480, 490, 50, 510, 520, 530, 540, 55, 560

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (0,0,0,0,2,0,0,0,0,-1).

Formula

G.f.: 5*x*(2 +4*x +6*x^2 +8*x^3 +x^4 +8*x^5 +6*x^6 +4*x^7 +2*x^8)/(1 -x^5)^2.

a(n) = 2*a(n-5) - a(n-10).

Mathematica

Table[If[Mod[n, 5]==0, n, If[Mod[10 n, 5]==0, 10 n, 10 n + 5 - Mod[10 n, 5]]], {n, 60}] (* or *) CoefficientList[Series[5 (2 + 4 x + 6 x^2 + 8 x^3 + x^4 + 8 x^5 + 6 x^6 + 4 x^7 + 2 x^8)/(1 - x^5)^2, {x, 0, 40}], x]

Prog

I:=[10, 20, 30, 40, 5, 60, 70, 80, 90, 10]; [n le 10 select I[n] else 2*Self(n-5)-Self(n-10): n in [1..60]];

Crossrefs

Cf. A082799, A082800, A082801, A082802, A082803, A082804.

Sequence in context: A172260 A300024 A069534 * A236507 A031140 A095973

Adjacent sequences: A237413 A237414 A237415 * A237417 A237418 A237419

Keyword

nonn,easy

Author

Vincenzo Librandi, Feb 10 2014

Status

approved